Designation D5114 − 90 (Reapproved 2010) Standard Test Method for Laboratory Froth Flotation of Coal in a Mechanical Cell1 This standard is issued under the fixed designation D5114; the number immedia[.]
Trang 1Designation: D5114−90 (Reapproved 2010)
Standard Test Method for
This standard is issued under the fixed designation D5114; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Froth flotation of coal, the separation of ash-bearing minerals from combustibles via differences in surface chemistry, has been steadily increasing in use as a means to treat 600-µm (No 30 U.S.A
Standard Sieve Series) or finer coal The process is one in which many variables need to be monitored
and regulated Because of this complexity, rigorous laboratory testing is difficult to standardize
This test method outlines the types of equipment and procedures to apply on a laboratory scale to isolate key process variables and minimize the variations associated with the design and execution of
a froth flotation test The objective of the test method is to develop a means by which repeatable
grade/recovery results are ascertained from froth flotation testing of coal without imposing
unnecessary limitations on the applicability of the test results in coal preparation practice
It is recognized that sample preparation, particularly comminution, has a significant impact on froth flotation response This test method does not attempt to define sample preparation and size reduction
practices as part of a froth flotation testing program
This test method also does not completely cover specific procedures for the investigation of flotation kinetics Such a test is specialized and is highly dependent upon the end use of the data
1 Scope
1.1 This test method covers a laboratory procedure for
conducting a single froth flotation test on fine coal (that is,
nominal top size of 600 µm (No 30 U.S.A Standard Sieve
Series) or finer) using a defined set of starting point conditions
for the operating variables
1.2 This test method does not completely cover specific
procedures for the investigation of flotation kinetics Such a
test is specialized and highly dependent upon the objective of
the data
1.3 Since optimum conditions for flotation are usually not
found at the specified starting points, suggestions for
develop-ment of grade/recovery curves are given inAppendix X1 Such
a procedure is very case-specific and involves running a series
of flotation tests in which some of the operating variables are
changed in order to optimize conditions for either yield or
grade
1.4 Laboratory flotation results need not be representative of
the flotation response of coal in full-scale situations, but a
consistent baseline can be established against which full-scale performance can be compared
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other Combining values from the two systems may result in non-conformance with the standard
1.6 This standard does not purport to address the safety
concerns, if any, associated with its use It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.7 Material Safety Data Sheets (MSDS) for reagents used are to be obtained from suppliers who are to be consulted before work with any chemicals used in this test method
2 Referenced Documents
2.1 ASTM Standards:2
D121Terminology of Coal and Coke D2013Practice for Preparing Coal Samples for Analysis
1 This test method is under the jurisdiction of ASTM Committee D05 on Coal
and Coke and is the direct responsibility of Subcommittee D05.07 on Physical
Characteristics of Coal.
Current edition approved Sept 1, 2010 Published January 2011 Originally
approved in 1990 Last previous edition approved in 2004 as D5114 – 90 (2004).
DOI: 10.1520/D5114-90R10.
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States
Trang 2D2015Test Method for Gross Calorific Value of Coal and
Coke by the Adiabatic Bomb Calorimeter (Withdrawn
2000)3
D2234/D2234MPractice for Collection of a Gross Sample
of Coal
D3173Test Method for Moisture in the Analysis Sample of
Coal and Coke
D3174Test Method for Ash in the Analysis Sample of Coal
and Coke from Coal
D3177Test Methods for Total Sulfur in the Analysis Sample
of Coal and Coke(Withdrawn 2012)3
D4239Test Method for Sulfur in the Analysis Sample of
Coal and Coke Using High-Temperature Tube Furnace
Combustion
D4749Test Method for Performing the Sieve Analysis of
Coal and Designating Coal Size
3 Terminology
3.1 Definitions—For definitions of terms used in this test
method, see TerminologyD121
3.2 Definitions of Terms Specific to This Standard:
3.2.1 collector—a reagent used in froth flotation to promote
contact and adhesion between particles and air bubbles
3.2.2 combustibles—the value obtained by subtracting the
dry weight (in percent) of the ash (as determined in Test
MethodD3174) from 100 % representing the original weight
of the analyzed sample
3.2.3 concentrate—the froth product recovered in coal froth
flotation
3.2.4 conditioning agents—all chemicals that enhance the
performance of the collectors or frothers Conditioning agents
change the characteristics of the surface of the minerals or the
environment There are many subgroups according to function:
activators, depressants, emulsifiers, dispersants, flocculants,
chelating reagents, froth depressants, pH modifiers, and so
forth
3.2.5 flotation cell—the vessel or compartment in which the
flotation test is performed
3.2.6 froth—a collection of bubbles and particles on the
surface of a pulp in a froth flotation cell
3.2.7 froth flotation—a process for cleaning fine coal in
which hydrophobic particles, generally coal, attach to air
bubbles in a water medium and rise to the surface to form a
froth The hydrophilic particles, generally the ash-forming
matter, remain in the water phase
3.2.8 frother—a reagent used in froth flotation to control the
size and stability of the air bubbles, principally by reducing the
surface tension of water
3.2.9 grade/recovery—the relationship between quality and
quantity of the clean coal product The quality can be defined
in terms of ash, sulfur, or Btu content The quantity can be
designated as yield or heating value recovery (Btu or
combus-tibles)
3.2.10 mechanical cell—a type of flotation cell that employs
mechanical agitation of a pulp by means of an immersed impeller (rotor) and stator stirring mechanism Aeration to the cell can be from an external pressurized air source or self-induced air
3.2.11 natural pH—the measured pH of the pulp prior to the
addition of collector, frother, or any conditioning agents
3.2.12 pulp—a fluid mixture of solids and water, also known
as slurry
3.2.13 recovery—the percent of the valuable component
(that is, Btu or combustible) from the feed that reports to the froth concentrate product
3.2.14 solids concentration—the ratio, expressed as a
percent, of the weight (mass) of solids to the sum of the weight
of solids plus water
3.2.15 tailings—the underflow product from coal froth
flo-tation
3.2.16 yield—the weight percent of the feed that reports to
the concentrate
4 Significance and Use
4.1 This test method uses specific starting point conditions for the froth flotation response to accomplish the following: 4.1.1 Assess responses of one or more coals or blends of coal, and
4.1.2 Evaluate and determine froth flotation circuit perfor-mance
5 Apparatus
5.1 Laboratory Flotation Machine, with a minimum volume
of 2 L and a maximum volume of 6 L Fig 1schematically
3 The last approved version of this historical standard is referenced on
Trang 3depicts a batch mechanical flotation cell4which can be used in
conjunction with this test method The major criterion is that
the unit must be able to provide for constant mechanical
removal of froth from the cell In addition, the laboratory unit
must have some means of automatic liquid level control
5.1.1 An example of a mechanical paddle laboratory froth
flotation apparatus is shown in Fig 1 The froth paddles are
rotated at approximately 30 r/min, thus avoiding variation
caused by manual removal of froth The froth paddle shall not
rotate below the pulp surface and not more than 6 mm (1⁄4in.)
above the pulp level The distance between the overflow lip and
the edge of the froth paddle shall be at least 3 mm (1⁄8in.) but
not more than 6 mm (1⁄4 in.)
5.1.2 The pulp in the cell is maintained at a constant level by
a small tank with an overflow at precisely the desired level to
be maintained in the flotation cell
N OTE 1—Another suitable slurry level control system consists of a
resistance type level probe, a resistance sensor relay, a solenoid valve, and
associated connecting wires 5 The level probe is mounted inside the cell
and is connected to the resistance relay which operates the solenoid valve.
When the slurry level drops below the tip of the probe, the relay energizes
the solenoid valve Then, makeup water flows into the cell When the level
rises up to the probe, the solenoid valve is de-energized, which stops the
makeup water flow.
5.2 pH Meter, sensitive to 0.1 units.
5.3 Timing Device that displays cumulative minutes and
seconds
5.4 Air Flow Meter.
5.5 Microsyringes or Pipets.
5.6 Balances, with a readability of at least 0.5 % of the total
weight
5.7 Vacuum or Pressure Filter, or a filter funnel for gravity
filtration
5.8 Drying Oven with forced air, capable of maintaining a
maximum temperature of 40°C (104°F) and meeting the
requirements of MethodD2013
5.9 Rinse Bottle.
6 Sample Preparation
6.1 The sample history, moisture content, alteration of the
inherent moisture, or alteration of the surface properties have
considerable effect on the flotation characteristics of the coal It
is important that all samples used in flotation testing are stored
and handled so as to minimize alteration of the surface
properties The origin and history of the sample should be
recorded It is imperative that all samples be prepared in a
similar manner Since the generation of grade/recovery curves
will involve several individual tests, sample subdivision and
preparation must be carefully performed to ensure that each
subsample is representative of the original whole sample
7 Flotation Conditions
7.1 The conditions under which a test program is conducted will be systematically varied to generate grade/recovery curves (Appendix X1).Table 1 outlines recommended starting point conditions for a single laboratory-scale test These conditions are for laboratory testing parameters and are not designed to simulate in-plant operating conditions that can be highly variable, such as water temperature and chemistry
7.2 Slurry Temperature—The operating temperature shall be
22 6 5°C (72 6 9°F)
7.3 Water—Plant, tap, or distilled water may be used,
whichever is consistent with the object of the test The source
of water must be recorded
7.4 Solids Content—The solids content corresponds with
that of the industrial preparation plant slurry, if the object of the test is to simulate plant conditions Otherwise, an 8 % solids concentration shall be used
7.5 Pulp Level—Maintain between 12.7 and 15.9 mm (0.50
and 0.62 in.) below the lip of the cell as measured with the air
on and stirrer operating
7.6 Wetting of Coal—Before the addition of reagents and
subsequent flotation, it is important to ensure that the proper air bubble attachment can take place at the coal-water interface Wetting is accomplished in the cell by running the impeller at the r/min specified for the flotation step with the air off Perform this step for 5 to 10 min before reagent addition If the sample is in slurry form this wetting step is not necessary
7.7 Reagent Addition—Collector, frother, conditioning
agent, or any combination thereof shall be governed by the requirements of the test Add reagents to the coal slurry and condition to ensure proper distribution of reagents Conduct the conditioning step at the same impeller speed as the flotation step with the air flow off
7.7.1 Add the reagents using either a calibrated microsy-ringe or a pipet
7.8 Air Flow—Rate shall be measured and recorded 7.9 Impeller Speed—The starting speed shall be 1200 r/min.
investigated during optimization, depending on the object of the test.
8 Procedure
8.1 Calculate the total mass of coal required for the number
of flotation tests based on the measured cell volume and the test solids content
8.2 Divide the total mass into representative portions by riffling, in accordance with Method D2013 A few small increments, totalling no more than 15 % of the total mass, may
be either taken from the subsample or added to the subsample
in order to obtain the exact weight
8.3 Determine the particle size distribution of one of the portions from 8.2in accordance with Test MethodD4749 8.4 Rinse the cell thoroughly with water Add from one half
to two thirds of the total required water to the cell Confirm that the air is turned off Turn the impeller on and adjust to the
4 A suitable cell, available from WEMCO, 1796 Tribute Rd., Sacramento, CA
95815, or equivalent can be used.
5 A suitable slurry level control system, available from C&R Technology, Inc.,
P.O Box 114, Fall Branch, TN 37656, or equivalent can be used.
Trang 4desired speed Transfer a sample into the cell Be careful to
remove all of the coal from the sides of the transfer container
Continue this wetting step for approximately 5 min Add most
of the additional water but reserve a sufficient quantity for
rinsing (see8.8)
8.5 Determine the pH and temperature of the slurry with the
air turned off
8.6 Start the timing device Add the collector to the slurry
and condition for 90 s After this first conditioning step, use a
small quantity of rinse water to wash down any coal that is
clinging to the sides of the cell
8.7 Again start the timer Add the frother to the slurry and
condition for 30 s
8.8 After this second conditioning step, wash down any coal
that is clinging to the sides of the cell At this time, the pulp
level shall be the operating level specified in7.5
8.9 Confirm that the water valve is open to the constant
level control system
8.10 Turn on the froth paddles and start the air flow
8.11 Start the froth collection timer when the air is turned
on
8.12 Collect the froth in a series of pans Continue
collect-ing the incremental froth produced for each of the
predeter-mined time periods or until the froth is no longer coal laden
(lack of black color to the froth), recording the time, T f, at
which this occurs (see Table 2)
8.13 Continually rinse the froth clinging to the sides of the
flotation cell into the pulp
8.14 At the end of the flotation period, close the valves to
the constant level control tank and air supply Rinse all material
adhering to the sides of the cell and stand pipe into the cell
Wash all material remaining on the cell lip and scraper paddles
into the concentrate
8.15 Separately dewater (usually by filtration), air dry, and
weigh each concentrate and tailing Refer to Method D2013
Determine the residual moisture, ash content, and any other
parameters required for each sample
9 Calculation
9.1 Calculate all parameters on a dry basis
9.2 Calculate yield, Y, in weight percent as follows:
Y 5 100 3 W c
W c 1W t
where:
W c = weight of froth concentrate, and
W t = weight of tailing
9.3 Calculate the percent recovery, A, of any analytical
parameter using the following formula, which uses the feed value reconstituted from the froth concentrate and tailing
A 5 Y 3 P c
P f
where:
P c = is one of the following:
A c = percent ash in the froth concentrate fraction,
S c = percent sulfur in the froth concentrate fraction,
B c = Btu/lb in the froth concentrate fraction, and
C c = percent combustible in the froth concentrate fraction, and
P f = is one of the following reconstituted feed parameters calculated from the froth concentrate fractions and the tailing (seeTable 2):
A f = percent ash in the feed,
S f = percent sulfur in the feed,
B f = Btu/lb in the feed, and
C f = percent combustible in the feed
9.4 Calculate the percent impurity reduction, A, for any
analytical parameter as follows:
A 5 P f 2 P c
P f 9.5 Calculate the weight percent of parameter removal, A,
for any analytical parameter as follows:
A 5~100 2 Y!3~P t!
P f
where:
Y and Pfare as defined above,
Ptis one of the following:
A t = percent ash in the tailing fraction,
S t = percent sulfur in the tailing fraction,
B t = Btu/lb in the tailing fraction, and
C t = percent combustible in the tailing fraction
9.6 Calculate the efficiency index, E, as follows:
E 5 Y 3 A t
A c
10 Report
10.1 A test report shall be issued containing the following information:
10.1.1 Sample identity and history, 10.1.2 Feed size distribution, 10.1.3 Reagent concentration of frother, collector, and con-ditioning agent,
TABLE 1 Starting Point Conditions for Laboratory Froth Flotation
of Coal
N OTE 1— Additional time can be required for a slowly responsive coal;
record any extra time.
Solids concentration 8 % solids
Total volume 2 to 6 L
Wetting time 5 min
Impeller speed 1200 r/min
Reagent additions and conditioning times:
1 Add collector
2 Condition for 90 s
3 Add frother
4 Condition for 30 s
Air flow rate 3 L/min per litre of pulp
Skimmer rotation 30 r/min
Collection increments 15, 30, 60, 90, 120, 240 (cumulative time
in seconds)
Trang 510.1.4 Wetting time,
10.1.5 Conditioning times,
10.1.6 Solids concentration,
10.1.7 Pulp pH,
10.1.8 Slurry temperature,
10.1.9 Air flow rate,
10.1.10 Weight of charge,
10.1.11 Impeller r/min,
10.1.12 Weight of concentrate fractions and tailings,
10.1.13 Collection time period(s), and
10.1.14 Source of water
10.2 Report ash, sulfur, Btu/lb, or combustible recovery and
yield data on the form shown inTable 2
11 Precision and Bias
11.1 Precision—The precision at the starting point
condi-tions is being investigated by a task group Other operating conditions are too numerous to establish precision statements
at this time
11.2 Bias—Pending an evaluation of this test procedure, the
absence of a reference material precludes a bias statement
12 Keywords
12.1 collector; flotation; flotation cell; froth flotation; frother; froth paddles; mechanical cell; pulp level; slurry level; starting point conditions
TABLE 2 Report
Test No.: _ Sample identity:
Froth Collection FractionAB
Tailing Cumulative Time
Dry weight of solids
w c (n) w t Weight recovery
Y(n) Y t Ash
A c (n) A t Sulfur
S c (n) S t Btu
B c (n) B t Btu recovery
R(n) R t Ash reduction
Z(n) Z t Sulfur reduction
V(n) V t
Last coal laden froth time, T f _ s
Feed Head Sample
Recombined Head Sample
Ash, dry weight percent A f
Sulfur, dry weight percent S f
A
Where:
f = feed,
n = nth timed froth increment sampled, and
t = tailing.
W f = W c (1) + W c (2) + + W c (n) + W t
A f = Y(1) *A c (1) + Y(2) *A c (2) + + Y c (n) *A c (n) + Y t *A t
S f = Y(1) *S c (1) + Y(2) *S c (2) + + Y c (n) *S c (n) + Y t *S t
B f = Y(1) *B c (1) + Y(2) *B c (2) + + Y c (n) *B c (n) + Y t *B t
B The mass of the reconstituted feed, W f , is the sum of the masses of the concentrated samples, W c (n), and the tailing, W t If W fdiffers greater than weight 3 % from the mass of the initial feed, then the data should be questioned.
Trang 6APPENDIX (Nonmandatory Information) X1 OPTIMIZATION CONSIDERATIONS
X1.1 The procedure outlined in this Appendix provides a
means of evaluating the flotation characteristics of a coal
through the manipulation of process variables to achieve a
grade/recovery relationship indicative of the separation that
may be expected from the froth flotation process for a given
coal at a given particle size distribution
X1.2 Laboratory froth flotation testing need not be
repre-sentative of flotation response of a particular coal in a full-scale
situation However, the grade/recovery curves generated from
laboratory procedures can be used to provide information
regarding how a coal reacts to changes in various operating
parameters The flotation of coal involves a complex
interac-tion of several factors, including:
X1.2.1 Flotation conditions,
X1.2.2 Surface characteristics, and
X1.2.3 Particle size distribution
X1.3 All of these factors can be varied to affect the flotation
characteristics of a given coal Among the flotation conditions
most often varied to understand and control flotation are the
following:
X1.3.1 Conditioning time,
X1.3.2 Flotation time,
X1.3.3 Reagent type,
X1.3.4 Reagent dosages,
X1.3.5 Air flow rates,
X1.3.6 pH of pulp, and
X1.3.7 Solids loading
X1.4 Individual flotation tests are required for reviews to
identify the effect of varying each of these parameters in an
effort to determine the best flotation conditions for a particular
coal This appendix contains procedures by which the
condi-tions can be systematically altered and subsequent flotation results presented for data evaluation
X1.5 Among the most common flotation tests performed in the laboratory are those in which flotation reagents are altered incrementally to evaluate the ideal dosages to be run in a preparation plant To produce data for evaluation in a grade/ recovery curve, a test plan can be formulated to conduct several individual flotation tests on equivalent splits of a coal sample Each, of these flotation tests would be run using this test method but with reagent dosages for each test correspond-ing to the test plan
X1.5.1 Example—It can be desirable to determine the effect
of the amount of fuel oil used to condition the surface of the coal on the ash reduction and thermal recovery of the coal To accomplish this, a test plan might be formulated in which a number of individual flotation tests would be run For instance, fuel oil dosages from 0.25 to 2.5 g/kg (0.5 to 5.0 lb/ton) varied
in 0.25-g/kg (0.5-lb/ton) increments can be used Each flotation test would be run according to this flotation standard and the results would be presented in the standard format shown in
Table 2 Flotation results generated by varying one or more parameters may be graphically depicted as presented in Fig X1.1andFig X1.2.6Fig X1.1shows where optimum pine oil addition occurs in the flotation of Mary Lee Seam coal X1.5.2 Such data is not definitive with respect to actual plant operation However, it does provide information about the ease and efficiency of processing any particular coal sample Evaluation of grade/recovery curves will assist in the determination of the course for further test work It should not
be viewed in and of itself as an indication of an intrinsic floatability of a coal, but as a reflection of the response of the coal to the specific levels of all process variables as presented
by this test procedure
6 See Chernosky, F J., “Evaluation of Coal Flotation Frothers on a
Yield-Selectivity Cost Basis,” Transactions of AIME, Vol 226, March 1963, pp 24–25.
Trang 7ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned
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FIG X1.1 Example of Consumption Curve for Mary Lee Coal
FIG X1.2 Example of Grade Versus Yield Curves for Mary Lee Coal